Statistics Exam 2- Ch. 5-7
A researcher selects from a participant pool of four males and six females. He determines that the probability of selecting two female participants is p = .30. Based on this probability, what strategy did the researcher use to sample participants? a. sampling with replacement b. sampling without replacement
b. sampling without replacement
Given the following values: = 10, M = 8, = 0.5, conduct a one-sample ztest at a .05 level of significance. What is the decision for a two-tailed test? a. to retain the null hypothesis b. to reject the null hypothesis c.There is not enough information since the sample size is not given.
b. to reject the null hypothesis
Which of the following is required to locate proportions of area under the normal curve? a. compute a z-transformation. b.find the probability of a z score in the unit normal table. c. both A and B d. none of these
c. both A and B
Which of the following is required to locate z scores with a given proportion? a.find the z score associated with a given probability b. compute a z transformation to find the raw score c. both A and B d. none of these
c. both A and B
A researcher obtains z = 3.98 for a one-sample z test. If her decision is to retain the null hypothesis, then what do you know about her decision? a. Her decision was inconclusive. b. both A and B c. Her decision was based on a two-tailed test. d. Her decision resulted in a Type III error.
d. Her decision resulted in a Type III error.
When reporting the results of a one-sample z test using APA format, the ______ does not need to be reported. a. effect size b. critical values c. p value d. test statistic
b. critical values
A researcher conducts a study, but has low power to detect an effect. Which of the following is one way in which the research can increase power? a. conduct the study again with the same sample size b. increase the sample size c. study a population with a larger standard deviation d. make the alpha level smaller
b. increase the sample size
What values are distributed along the x-axis for a sampling distribution of the sample variance? a. both B and C b. sample variances c. scores d. sample means
b. sample variances
______ allows researchers to describe (1) how far mean scores have shifted in the population or (2) the percentage of variance that can be explained by a given variable. a. Probability b. Power c. Effect size d. Significance
c. Effect size
State whether the first area is bigger, the second area is bigger, or the two areas are equal: the area to the left of z = 0.80, or the area to the right of z = -0.80. a. The second area is bigger. b. The two areas are the same. c. The first area is bigger.
b. The two areas are the same.
A researcher determines that students study an average of 80 ± 20 (M± SD) minutes per week. Assuming these data are normally distributed, what is the z score for students studying 60 min per week? a. 0.1587 b. 0.3413 c. -1.0 d. 1.0
c. -1.0
A researcher selects a sample of 100 participants from a population with a mean of 38 and a standard deviation of 20. About 68% of the sample means in this sampling distribution should be between a sample mean of ______. a. 36 and 40 b. 34 and 38 c. 38 and 44 d. 18 and 58
a. 36 and 40
Suppose you select a sample of three people from a population of four (A, B, C, D). Which of the following samples is possible using the experimental sampling strategy? a. persons B, C, and D b. persons A, D, and D c. persons A, C, and A d. persons B, A, and B
a. persons B, C, and D
Suppose a researcher wants to make sure that the probability of committing a Type I error is less than 5%. How can the researcher control for this? a. set the alpha level at .05 b. set the value for a Type II error at .05 c. place the rejection region in both tails d. both B and C
a. set the alpha level at .05
How is the standard error of the mean typically reported in a graph? a. using error bars b. it is never reported in a graph c. by plotting sample means d. by listing group names along the x-axis
a. using error bars
Which of the following statements regarding the null hypothesis is true? a.The null hypothesis always makes statements about a population parameter. b.A decision in hypothesis testing is made about the alternative hypothesis, not the null hypothesis. c.The null hypothesis is the only hypothesis stated in hypothesis testing. d. all of these
a.The null hypothesis always makes statements about a population parameter.
A researcher records the following times (in seconds) that it took a group of students to complete an exam: 18 ± 2 min (M ± SD). How long did it take 80% of students to complete the exam? a. 16.32 min b. 19.68 min c. less than 16 min d. less than 18 min
b. 19.68 min
The following samples were selected by two researchers. Which is associated with a smaller standard error of the mean? Researcher A: n = 25, = 5, = 7 Researcher B: n = 25, = 32, = 7 a. Researcher A b. They both have the same standard error. c. Researcher B
b. They both have the same standard error.
A measure of the size of an effect in a population is called ______. a. significance b. effect size c. probability d. power
b. effect size
In hypothesis testing, a researcher's decision ______. a. is based on a probability b.depends on the level of significance for a hypothesis test c. can be to retain or reject the null hypothesis d. all of these
d. all of these
What is the implication for the tails of a normal distribution being asymptotic? a.that there are an infinite number of possible normal distributions b.that scores above the mean are distributed the same as scores below the mean c. that this characteristic has no practical implication d.that extreme scores are possible in the tails of a normal distribution
d. that extreme scores are possible in the tails of a normal distribution
The total number of possible outcomes for a random variable is referred to as ______. a. probability b. the sum c. a random event d. the sample space
d. the sample space
A theoretical distribution that evenly distributes data around the mean, median, and mode is called the ______. a. normal distribution b. bell-shaped distribution c. Gaussian distribution d. all of these
d. all of these
Which of the following is a possible value for the standard deviation of a normal distribution? a. - b. 0.5 c. 0 d. -2
b. 0.5
A researcher records the following number of birdcalls made during an experimental session with robins: 7.2 ± 0.6 (M ± SD). Assuming these data are normally distributed, what is the probability that robins made more than nine birdcalls during this experimental session? a. .0013 b. .9987 c.The probability is not listed in the unit normal table. d. .4987
a. .0013
An article states that a sample of 40 participants took 12 ± 2.3 (M ± SEM) s to complete a cognitive assessment. Which value is the standard error of the mean? a. 2.3 b. 40 c.The standard error of the mean is not reported in the article. d. 12
a. 2.3
A researcher records the following assessment data: 42 ± 6 (M ± SD). The researcher only wants to sample participants scoring in the top 20% of this assessment. What is the cutoff score for the top 20% in this example? a. 0.84 b. 47.04 c.There is not enough information to answer this question. d. 36.96
b. 47.04
Which type of sampling is most often applied by researchers in the behavioral sciences? a. experimental sampling b. standard normal sampling c. normal sampling d. theoretical sampling
a. experimental sampling
A researcher believes that increasing attention given to children will improve mean academic performance. Therefore, the alternative hypothesis should be ______. a. mean academic performance will increase b. mean academic performance will not change c. mean attention will increase d. mean academic performance will decrease
a. mean academic performance will increase
Based on the effect size conventions, d = 0.60 is a ______. a. medium effect size b. large effect size c. small effect size
a. medium effect size
The proportion or fraction of times an outcome is likely to occur is referred to as ______. a. probability b. luck c. a random event d. sample space
a. probability
A researcher obtains z = 1.45 for a one-sample z test. What is the decision for this test at a .05 level of significance? a. to retain the null hypothesis b.It depends on whether the test is one-tailed or two-tailed. c. There is not enough information to make a decision. d. to reject the null hypothesis
a. to retain the null hypothesis
A researcher increases the sample size, which will ______. a. increase variability in the population b. decrease the value of standard error c. reduce variability in the population d. increase the value of standard error
b. decrease the value of standard error
Based on the effect size conventions, d = 0.18 is a ______. a. medium effect size b. large effect size c. small effect size
c. small effect size
What is the typical level of significance for a hypothesis test in behavioral research? a. .001 b. .10 c. .50 d. .05
d. .05
A researcher selects a sample of 9 participants from a population with a mean of 8 and a standard deviation of 3. About 14% of the sample means in this sampling distribution should be between a sample mean of ______. a. 5 and 6 b. 10 and 11 c. 6 and 8 d. 9 and 10
d. 9 and 10
A researcher randomly selects a sample of athletes and reports that their average score on a health and fitness scale is 23. Based on the characteristics of the sample mean, what does this say about the mean in the population? a.There is no way to know without knowing the size of the sample. b. Nothing; it was just a sample. c.It tells us that the mean in the population is no less than 23. d.We expect that the population mean is equal to 23 because the sample mean is an unbiased estimator of the population mean.
d. We expect that the population mean is equal to 23 because the sample mean is an unbiased estimator of the population mean.
A researcher finds that the average preschool-aged child drinks two cups of milk per day. Assuming these data are normally distributed, the z score for the average cups per day in this example is ______. a. less than 0 b.there is not enough information to answer this question c. greater than 0 d. exactly equal to 0
d. exactly equal to 0
A researcher obtains z = -6.45. What is the decision for a one-tailed test, upper-tail critical, at a .05 level of significance? a. to reject the null hypothesis b. There is not enough information to make a decision. c. It depends on the sample size. d. to retain the null hypothesis
d. to retain the null hypothesis
A therapist has a goal to reduce the mean number of patient symptoms expressed for a particular disorder to two symptoms per day. Following therapy, she determines that the z score for two symptoms per day is 0. Assuming these data are normally distributed, did she reach her goal? a. Yes, because a z score of 0 is the average, or mean. b.No, because the z score is not negative (indicating a reduction in symptoms). c. No, because the z score indicates 0 improvement. d.Yes; in fact, she actually reduced the mean number of symptoms to 0.
a. Yes, because a z score of 0 is the average, or mean.
The sampling distribution of the mean and the sampling distribution of the variance (when dividing SS by n - 1) ______. a. are both unbiased estimators b. both follow the central limit theorem c. are both associated with minimal variance d. all of these
a. are both unbiased estimators
The one-sample z test is a hypothesis test used to test hypotheses ______. a. concerning a single population with a known variance b. concerning at least one population c. concerning the variance in a population d. all of these
a. concerning a single population with a known variance
As sample size increases, the standard error of the mean ______. a. decreases b. can increase or decrease c. does not change d. increases
a. decreases
The mean of the sampling distribution of sample means is ______. a. equal to the population mean b. equal to the population variance c. both A and B d. none of these
a. equal to the population mean
A researcher visits a population of 1,200 local residents to determine the proportion of local residents who support a new smoking ban. In this case, the sample space is ______. a. equal to the population of 1,200 local residents b. unknown c. equal to the number of local residents who smoke d.equal to the number of residents who support the new smoking ban
a. equal to the population of 1,200 local residents
In Step 2 of hypothesis testing, researchers state a level of significance to minimize the probability of ______. a. rejecting a true null hypothesis b. retaining a false null hypothesis c. inflating the power of a decision d. all of these
a. rejecting a true null hypothesis
A researcher selects a sample of size 6 from a population of size 10. How many possible samples of this size can be selected using theoretical sampling? a. over 60,000,000 samples b. 1,000,000 c. 100,000 d. 10,000,000
b. 1,000,000
A professor finds that the students scored a 76 ± 8 (M ± SD) on the final exam. On this exam, a score of 90 is an A. Assuming these data are normally distributed, what is the z score for 90 (the cutoff for an A)? a. 1.50 b. 1.75 c. 1.25 d.There is not enough information to answer this question.
b. 1.75
A researcher selects a sample of 36 students from a school population with a mean IQ of 100 and standard deviation of 12. She determines that the mean IQ in this sample is 104. Assuming she computes a one-sample z test at a .05 level of significance, what is the decision for a two-tailed test? a.Retain the null hypothesis; IQ scores in this sample are the same as those in the population. b.Reject the null hypothesis; IQ scores in this sample are significantly higher than those in the population. c. There is not enough information to make a decision.
b. Reject the null hypothesis; IQ scores in this sample are significantly higher than those in the population.
A researcher records the following body mass index (BMI) scores for a group of participants: 28.4 ± 1.6 (M ± SD). Participants who score between 25 and 30 on this scale are categorized as overweight. What percentage of participants fell in this overweight category? a. .8247 b. .8413 c. .1753 d. .4834
a. .8247
A researcher measures the number of tasks completed by participants during a 5-min multitasking session. If the number of tasks completed is distributed normally as 6.3 ± 1.0 (M ± SD) tasks, then what is the probability that participants completed less than 8 tasks? a. .9554 b. .4554 c.The probability is not listed in the unit normal table. d. .0446
a. .9554
A professor records the following final exam scores: 78 ± 7 (M ± SD). Students scoring in the top 14% get an A. What is the cutoff score for the top 14% in this example? a. 85.56 b.There is not enough information to answer this question. c. 70.44 d. 1.08
a. 85.56
A researcher directly controls for the probability of a ______, but does not directly control for the probability of a ______. a. Type II error; Type I error b. Type I error; Type II error c. Type II error; beta level d. Type I error; alpha level
b. Type I error; Type II error
Regardless of the distribution of the population, the sampling distribution of sample means will be approximately normally distributed. What characteristic of the mean explains this? a. unbiased estimator b. central limit theorem c. minimal variance d. none of these
b. central limit theorem
Which of the following is not one of the four steps to hypothesis testing? a. compute the test statistic b. identify hypothetical data c. set the criteria for a decision d. state the hypotheses
b. identify hypothetical data
Given the following values: u= 6.0, M = 7.6, n = 36, o= 6, conduct a one-sample z test at a .05 level of significance. For a one-tailed test, upper-tail critical, what is the decision? a.There is not enough information since the sample size is not given. b. to retain the null hypothesis c. to reject the null hypothesis
b. to retain the null hypothesis
A researcher selects a sample of 25 participants from a population with a mean of 10 and a standard deviation of 5. What is the probability of selecting a sample mean that is at least two standard deviations larger than the population mean? a.equal to the probability of selecting a sample mean that is at least two standard deviations below the mean b. .4772 c. .0228 d. .9772
c. .0228
A researcher selects a sample of 121 participants from a population with a mean of 32 and a standard deviation of 22. What is the standard error of the mean? a. 32 b. 0.5 c. 2.0 d.There is not enough information to answer this question.
c. 2.0
A researcher records the following times (in seconds) that it took a group of mice to complete a maze: 23 ± 4.1 (M ± SD). The top 10% of mice finishing with the fastest times will be placed in a "maze bright" group. What is the cutoff time to be placed in this group? a.There is not enough information to answer this question. b. 17.75 s c. 28.25 s d. faster than 16 s
c. 28.25 s
A researcher reports that the size of an effect in some population is d = 0.88. Which of the following is an appropriate interpretation for d? a. The effect observed in the population was significant. b.Mean scores were significant by 0.88 points in the population. c.Mean scores shifted 0.88 standard deviations in the population. d.Mean scores were significant by 0.88 points in the sample.
c. Mean scores shifted 0.88 standard deviations in the population.
The ______ converts any normal distribution with any mean and anyvariance to a standard normal distribution with a mean of 0 and variance of 1. a. normal distribution b. unit normal table c. standard normal transformation d. standard normal distribution
c. standard normal transformation
Which of the following allows researchers to use the standard normal distribution to estimate the probability of selecting sample means? a.the fact that sample means vary minimally from the population mean b.the fact that increasing sample size will decrease standard error c. the central limit theorem d. the skewed distribution rule
c. the central limit theorem
A researcher has participants choose between three advertisements. She finds that 54 prefer Ad A, 86 prefer Ad B, and 60 prefer Ad C. The probability or proportion of participants preferring Ad B is ______. a. .60 b. 86 c. .86 d. .43
d. .43
Which of the following is NOT a characteristic of probability? a. Probability can never be negative. b. Probability varies between 0 and 1. c. Probability can be stated as a fraction or decimal. d. Probability is most useful for describing fixed events.
d. Probability is most useful for describing fixed events.
A researcher selects two samples of 64 participants each. In the first sample, the population mean was 10 and the variance was 16. In this second sample, the population mean was 25 and the variance was 9. Which sample will be associated with a larger standard error of the mean? a.None, both samples will have the same value for standard error. b.There is not enough information to answer this question. c. Sample 2 d. Sample 1
d. Sample 1
Because the sampling distribution of sample means is normally distributed, we can use the z transformation formula to find probabilities. Which of the following gives the appropriate notation for this formula? a. z= b. z= c. z= d. all of these
d. all of these
The unit of measurement distributed along the x-axis of a standard normal distribution is referred to as a ______. a. standardized score b. normalized deviation c. x score d. z score
d. z score
Which of the following describes the largest proportion in a zdistribution? a. The proportion of area above the mean. b. The proportion of area between z = +1 and z = -1. c. The proportion of area greater than z = 1.0. d. The proportion of area less than z = 0.
b. The proportion of area between z = +1 and z = -1.
A researcher selects from a participant pool of four males and six females. He determines that the probability of selecting two male participants is p = .16. Based on this probability, what strategy did the researcher use to sample participants? a. sampling without replacement b. sampling with replacement
b. sampling with replacement
The first step to hypothesis testing requires that a researcher ______. a. conduct a study b. state the hypotheses c. make a decision d. compute a test statistic
b. state the hypotheses
Experimental research is typically conducted using a sampling strategy in which ______. a. the order of selecting participants matters b.the same participant can never be selected twice in the same sample c. participants are replaced after being sampled d. all of these
b. the same participant can never be selected twice in the same sample
What is the z score for scores in the bottom 10%? a. -1.28 b. 2.32 c. 1.28 d. -2.32
a. -1.28
A researcher states that a sample of 100 shoppers spend 112 ± 40 (M ± SEM) dollars on groceries each week. Which value is the standard error of the mean? a. 40 b.The standard error of the mean is not reported in the article. c. 112 d. 100
a. 40
Scores far from the mean are located in the ______ of a normal distribution. a. tails b. most uncertain areas c. body d. most sensitive areas
a. tails
A method for testing a claim or hypothesis about a parameter in a population, using data measured in a sample, is called ______. a. guessing b. random sampling c. hypothesis testing d. level of significance
c. hypothesis testing
The following distribution most closely approximates a ______. a. positively skewed distribution b. negatively skewed distribution c. normal distribution d. multimodal distribution
c. normal distribution
What is the z score for scores in the top and bottom 2.5%? a. 1.96 b. ±0.675 c. ±1.96 d.0.0124
c. ±1.96
What is the z score for scores in the top 2.5%? a. 0.675 b. +1.96 c. 0.0124 d. 0.0250
b. +1.96
A researcher selects a sample of size 4 from a population of size 6. How many possible samples of this size can be selected using experimental sampling? a. 1,296 b. 30 c. 4,096 d. 15
d. 15
The normal distribution is symmetrical, which means that ______. a. this characteristic has no practical implication b.there are an infinite number of possible normal distributions c. extreme scores are possible in a normal distribution d.scores above the mean are distributed the same as scores below the mean
d. scores above the mean are distributed the same as scores below the mean
Hypothesis testing is also called ______. a. effect size b. random testing c. Type III error d. significance testing
d. significance testing
If a researcher obtains a null finding, then what is the decision? a. They correctly retained the null hypothesis. b. They failed to make a decision. c. They incorrectly rejected the null hypothesis. d. They correctly rejected the null hypothesis.
a. They correctly retained the null hypothesis.
When a researcher decides to retain the null hypothesis because the rejection region was located in the wrong tail, this is called a ______. a. Type III error b. Type I error c. Type II error d. correct decision
a. Type III error
The probability of committing a Type I error is stated by ______ and the probability for committing a Type II error is stated by ______. a. alpha; beta b. the power; the power c. beta; alpha d. a p value; a p value
a. alpha; beta
If the value of the test statistic is in the rejection region, then ______. a. p < .05 b. the decision is to reject the null hypothesis c.the value of the test statistic is larger than the critical value d. all of these
d. all of these
A therapist goes through her records and finds that 200 of her 400 patients showed significant improvement in mental health over the past year. Hence, the probability of her patients showing significant improvement in mental health is ______. a. 200 b. 0.50 c. 400 d. 0.05
b. 0.50
The following samples were selected by two researchers. Which is associated with a smaller standard error of the mean? Researcher A: n = 18, = 8, = 2.4 Researcher B: n = 12, = 8, = 2.4 a. Researcher A b. Researcher B c. They both have the same standard error.
a. Researcher A
A researcher computes a one-sample z test in two studies. Both studies used the same alpha level, placed the rejection region in both tails, and measured the same sample mean. The researcher selects a sample of 30 participants in Study 1 and decides to retain the null hypothesis. She selects a sample of 60 participants in Study 2 and decides to reject the null hypothesis. Which of the following is the best explanation for why the decision was different in Study 1 and Study 2? a.The different decisions in Study 1 and Study 2 are possible because the second test was associated with greater power to detect an effect. b.The different decisions in Study 1 and Study 2 are not possible because all values were the same. c.The different decisions in Study 1 and Study 2 are due to an error the researcher made in the first hypothesis test. d.The different decisions in Study 1 and Study 2 are not possible because the researcher tested the same hypothesis.
a. The different decisions in Study 1 and Study 2 are possible because the second test was associated with greater power to detect an effect.
State whether the first area is bigger, the second area is bigger, or the two areas are equal: the area to the left of z = 1.00, or the area to the left of z = -1.00. a. The first area is bigger. b. The two areas are the same. c. The second area is bigger.
a. The first area is bigger.
Based on the effect size conventions, d = 0.90 is a ______. a. large effect size b. small effect size c. medium effect size
a. large effect size
The power of the decision-making process is ______. a. the likelihood of rejecting a false null hypothesis b. the likelihood of committing a Type I error c. the same as a null finding d. stated by an alpha level
a. the likelihood of rejecting a false null hypothesis
A researcher reports that scores were higher than the mean in the population, z = 1.60, p = .05 (d = .14). If this was a test at a .05 level of significance, then what value must be incorrectly reported? a. the p value b. the effect size c. the alpha level d. the test statistic
a. the p value
A researcher obtains z = 1.80 for a one-sample z test. What is the decision for this test at a .05 level of significance? a.It depends on whether the test is one-tailed or two-tailed. b. to retain the null hypothesis c. to reject the null hypothesis
a.It depends on whether the test is one-tailed or two-tailed.
A researcher determines that students are active about 60 ± 12 (M ± SD) minutes per day. Assuming these data are normally distributed, what is the z score for students being active 48 min per week? a.There is not enough information to answer this question. b. -1.0 c. 1.0 d. 0
b. -1.0
A researcher records the following response times to a visual stimulus: 23 ± 3.1 (M ± SD) seconds. Assuming these data are normally distributed, what is the probability that participants responded in 20 s or less? a. .3340 b. .1660 c.The probability is not listed in the unit normal table. d. .6660
b. .1660
Which of the following best describes the p value? a. It is the same as an alpha level. b. It is a conditional probability. c.Its value must be greater than .05 to reject the null hypothesis. d. all of these
b. It is a conditional probability.
Is a one-sample z test reported differently for one-tailed and two-tailed tests? a. It depends on whether the results were significant. b. No, the same values are reported. c.Yes, only significant results for a two-tailed test are reported. d.It can be reported differently when the effect size is large.
b. No, the same values are reported.
A researcher conducts two studies. Each study was a one-sample z test. Both studies placed the rejection region in both tails and measured the same sample mean. The beat level in Study 1 was larger than the beta level used in Study 2. Which study is associated with greater power to detect an effect? a. They are associated with the same level of power. b. Study 2 c. Study 1
b. Study 2
A researcher computes a test statistic and finds that the p value for this test is .03. What does this result mean? a.The probability of committing a Type II error if we reject the null hypothesis is 3%. b.There is a 3% likelihood of obtaining the test statistic value, if the null were true. c.The probability of committing a Type I error if we retain the null hypothesis is 3%. d.There is a 3% likelihood that the researcher's hypothesis is correct.
b. There is a 3% likelihood of obtaining the test statistic value, if the null were true.
A researcher records the following time spent sleeping per night (in hours) in a group of participants: 5.8 ± 1.8 (M ± SD). The researcher decides to categorize participants who sleep between 6 and 8 hr as moderate sleepers. What percentage of participants fell in this category? a. about 7% b. about 35% c. about 39% d. about 11%
b. about 35%
Most behavior is believed to ______ a normal distribution. a. be exactly equal to b. approximate c. not resemble at all
b. approximate
Which of the following is not a step to locate a proportion in a normal distribution? a. transform a raw score (x) into a z score b. convert a proportion to a standard normal z score c.locate the corresponding proportion for the z score in the unit normal table
b. convert a proportion to a standard normal z score
A researcher selects a sample of 25 participants from a population with a mean of 10 and a standard deviation of 5. What is the probability of selecting a sample mean equal to at least 12? a. less than 1% b.equal to the probability of selecting a sample mean that is at most equal to 8 c. greater than 50% d.about the same as selecting a sample mean that is at least equal to the population mean
b. equal to the probability of selecting a sample mean that is at most equal to 8
A researcher selects a sample of 49 participants from a population with a mean of 12 and a standard deviation of 3.5. What is the probability of selecting a sample mean of 13 or larger from this population? a. about one standard deviation below the mean b. less than .03 c. greater than .31 d.equal to the probability of selecting a score above the mean
b. less than .03
The criterion for a decision regarding the value stated in a null hypothesis is set by the ______. a. both A and B b. level of significance c. p value d. probability value
b. level of significance
The shape of the sampling distribution of the mean is approximately ______, whereas the shape of the sampling distribution of the variance is approximately ______. a. positively skewed; normal b. normal; positively skewed c. normal; normal d. positively skewed; positively skewed
b. normal; positively skewed
What are the two decisions that researchers can make in hypothesis testing? a. accept or reject the null hypothesis b. retain or reject the null hypothesis c. both A and B are correct
b. retain or reject the null hypothesis
What is the central limit theorem? a.It explains that sample means will vary minimally from the population mean. b.It explains that a sampling distribution of possible sample means is approximately normally distributed, regardless of the shape of the distribution in the population. c.It explains that if we select a sample at random, then on average we can expect the sample mean to equal the population mean. d. all of these
b.It explains that a sampling distribution of possible sample means is approximately normally distributed, regardless of the shape of the distribution in the population.
Two researchers select a sample for a population with a mean of 12.4 and a standard deviation of 9. Researcher A selects a sample of 30 participants. Researcher B selects a sample of 40 participants. Which sample is associated with a smaller standard error? a.Researcher A's, because the sample size was larger. b.Researcher B's, because the sample size was larger. c.Researcher B's, because the sample size was smaller. d.Researcher A's, because the sample size was smaller.
b.Researcher B's, because the sample size was larger.
What is the z score for scores in the bottom 5%? a. 1.645 b. 0.4801 c. -1.645 d. The score is not listed in the table.
c. -1.645
A researcher selects a sample of 64 participants from a population with a mean of 10 and a variance of 16. What is the standard error of the mean? a. 10 b.There is not enough information to answer this question. c. 0.5 d. 2.0
c. 0.5
The standard normal distribution is normally distributed with a mean of ______ and a variance of ______. a. any positive value; any value b. any value; any positive value c. 0; 1 d. 1; 0
c. 0; 1
A news poll showed that voters had no preference for either of three candidates. In this example, the probability of a vote for, say, Candidate A equals ______. a. 1/2 b. 1.00 c. 1/3 d. 2/3
c. 1/3
A researcher reports the following result for a one-sample z test at a .05 level of significance: z = 1.88, p = -.06 (d = .25). Is this result significant? a. Yes, the decision is to reject the null hypothesis. b. No, because the effect size is small hypothesis. c. No, the decision is to retain the null hypothesis. d. Yes, because the effect size is large hypothesis.
c. No, the decision is to retain the null hypothesis.
Two normal distributions are observed. The first distribution has a mean of 12 and a standard deviation of 2. The second distribution has a mean of 0 and a standard deviation of 2. For which distribution will the z score for the mean be larger? a. the second distribution b. the first z distribution c. None, the z score will be the same.
c. None, the z score will be the same.
A researcher reports that the standard deviation in Population A is = 2.3 and the standard deviation in Population B is = 4.3. Which population is associated with the highest power to detect an effect? a. They are associated with the same level of power. b. Population B c. Population A
c. Population A
A researcher reports that the size of an effect in Population A is d = 0.10 and the effect size in Population B is d = 0.34. Which population is associated with greater power to detect an effect? a. Population A b. They are associated with the same level of power. c. Population B
c. Population B
The following samples were selected by two researchers. Which is associated with a smaller standard error of the mean?Researcher A: n = 36, u= 12, o= 9Researcher B: n = 36, u= 12, o= 6 a. They both have the same standard error. b. Researcher A c. Researcher B
c. Researcher B
State whether the first area is bigger, the second area is bigger, or the two areas are equal: the area to the right of the mean, or the area between z = ±1.00. a. The first area is bigger. b. The two areas are the same. c. The second area is bigger.
c. The second area is bigger.
A distribution of all sample means or sample variances that could be obtained in samples of a given size from the same population is called ______. a. a conditional procedure b. random sampling c. a sampling distribution d. sampling without replacement
c. a sampling distribution
A researcher selects a sample of 49 participants from a population with a mean of 12 and a standard deviation of 3.5. What is the probability of selecting a sample mean that is at least equal to the population mean? a. .50 b.equal to the probability of selecting a sample mean that is at most equal to the population mean c. both A and B d. none of these
c. both A and B
Increasing sample size will ______. a. increase the alpha level b. increase the likelihood of committing a Type I error c. increase the power of the decision d. all of these
c. increase the power of the decision
A researcher randomly selects a sample of participants from a population with a variance of 4. If a researcher selects a sample of 16 participants with a mean of 12, then what is the mean and standard error for the sampling distribution of the mean? a.There is not enough information to answer this question. b. mean = 12, standard error = 2 c. mean = 12, standard error = 0.5 d. mean = 12, standard error = 1
c. mean = 12, standard error = 0.5
In hypothesis testing, a researcher can never ______. a. make decisions about the null hypothesis b.know the likelihood of obtaining a sample mean if the null hypothesis were true c. prove that his or her hypothesis is correct d. compute a test statistic before making a decision
c. prove that his or her hypothesis is correct
The normal distribution has all of the following characteristics, exceptthat ______. a. it is symmetrical b. its distribution is theoretical c. the total area under the curve is greater than 1.0 d. the mean, median, and mode are equal
c. the total area under the curve is greater than 1.0
A researcher obtains z = 2.04 for a one-sample z test. What is the decision for this test at a .05 level of significance? a. to retain the null hypothesis b. There is not enough information to make a decision. c. to reject the null hypothesis d. It depends on whether the test is one-tailed or two-tailed.
c. to reject the null hypothesis
Which of the following is not a step to locate a score in a normal distribution? a. transform the z score into a raw score (x) b.locate a z score associated with a given proportion in the unit normal table c. transform a raw score (x) into a z score
c. transform a raw score (x) into a z score
What does it mean to say that the sample mean is an unbiased estimator of the population mean? a.The sample means will vary minimally from the population mean. b.The sampling distribution of possible sample means is approximately normally distributed, regardless of the shape of the distribution in the population. c.If we select a sample at random, then on average we can expect the sample mean to equal the population mean. d. all of these
c.If we select a sample at random, then on average we can expect the sample mean to equal the population mean.
A researcher selects two samples of 25 participants each. In the first sample, the population mean was 32 and the variance was 8. In this second sample, the population mean was 4 and the variance was 8. Which sample will be associated with a larger standard error of the mean? a. Sample 1 b. Sample 2 c.None, both samples will have the same value for standard error d.There is not enough information to answer this question.
c.None, both samples will have the same value for standard error
Each of the following statements are true, except that ______. a.the larger the standard deviation in the population, the larger the standard error b.the smaller the sample size, the larger the population size c.the larger the sample size, the larger the standard error d.increasing the sample size will decrease standard error
c.the larger the sample size, the larger the standard error
The mean can take on any value and the standard deviation can take on any positive value. Therefore, ______. a. this characteristic has no practical implication b.scores above the mean are distributed the same as scores below the mean c.there are an infinite number of possible normal distributions d. extreme scores are possible in a normal distribution
c.there are an infinite number of possible normal distributions
A professor finds that the average SAT score among all students attending his college is 1150 150 ( ). He polls his class of 25 students and finds that the average SAT score is 1,200. Suppose he computes a one-sample ztest at a .05 level of significance. What is his decision? a. to retain the null hypothesis b. to reject the null hypothesis c.to reject the null hypothesis for an upper-tailed test, but to retain the null hypothesis for a two-tailed test d.to reject the null hypothesis for a two-tailed test, but to retain the null hypothesis for an upper-tailed test
c.to reject the null hypothesis for an upper-tailed test, but to retain the null hypothesis for a two-tailed test
A counselor records the number of disagreements (per session) among couples during group counseling sessions. If the number of disagreements is distributed normally as 4.4 ± 0.4 (M ± SD) disagreements, then what proportion of couples disagree at least 4 times during each counseling session? a. .3413 b.The probability is not listed in the unit normal table. c. .1587 d. .8413
d. .8413
A sampling distribution of the sample mean or variance is ______. a.a distribution of all scores that could be obtained in a population b.a distribution of all scores that could be obtained in samples of a given size from one or more populations c.a distribution of all measures that could be obtained in a given sample of a given size d.a distribution of all sample means or sample variances that could be obtained in samples of a given size from the same population
d. a distribution of all sample means or sample variances that could be obtained in samples of a given size from the same population
By definition, the probability of an outcome or event is ______. a.the proportion of times an outcome is likely to occur b. the fraction of times an outcome is likely to occur c.particularly useful for predicting the likelihood of random events d. all of these
d. all of these
In a normal distribution, 50% of all data ______. a. fall above the mean b. fall below the median c. fall above and below the mode d. all of these
d. all of these
In terms of characterizing samples, statistical theory was developed using a sampling strategy in which ______. a. the order of selecting participants matters b.the same participant can be selected twice in the same sample c. participants are replaced after being sampled d. all of these
d. all of these
Researchers state a level of significance in terms of an alpha level. The alpha level indicates ______. a. the probability of committing a Type I error b.the probability of incorrectly rejecting the null hypothesis c. the probability value for the rejection region d. all of these
d. all of these
Which of the following is a scenario in which increasing sample size will increase power ______. a. when the effect size is small b. when the effect size is large c. when the probability of a Type I error is small d. all of these
d. all of these
It happens to be the case that the standard error of the sampling distribution of sample means ______. a. both A and C b. gets larger as the sample size increases c.is approximately equal to that in the population d. is minimal
d. is minimal
What values are distributed along the x-axis for a sampling distribution of the sample mean? a. scores b. sample variances c. both B and C d. sample means
d. sample means
A distribution of z scores are distributed in what type of unit of measurement? a. binomial outcomes b. probabilities c. depends on the shape of the distribution d. standard deviation units
d. standard deviation units
A professor gives an exam in which the mean score is 78 points. She gives another exam to test whether or not scores change. In this example, the null hypothesis is ______. a. M = 78 b. M ?0 ‚ 78 c. u? ‚ 78 d. u= 78
d. u= 78
A parent decides to reward her child if he eats an average of at least five bites of his vegetables at dinner during the first week. She finds that her child ate 4 ± 0.8 (M ± SD) bites per meal for the first week. Assuming these data are normally distributed, should this parent reward her child? a.Yes, because the z score for 5 bites is less than 0. b.Yes, because the z score for 5 bites is greater than 0. c. No, because the z score for 5 bites is less than 0. d.No, because the z score for 5 bites is greater than 0.
d.No, because the z score for 5 bites is greater than 0.
